Access element



Oct. 26, 1937. J, M. G, FULLMAN 2,097,394'

ACCESS ELEMENT Filed Dec. 10, 1935 Patented Oct. 26, 1937 UNITED STATES ATENT ..FFEC

ACCESS ELEMENT poration of Delaware Application December 10, 1935, Serial No. 53,763

6 Claims.

This invention relates to an access element for use in underfloor ducts.

In installing underfloor ducts for the reception of electrical wiring, access must be had through the floor to the body of the conduit in order to install and make connection to receptacles or appliances, as it may from time to time be desirable to give outlet in different localities along the length of the duct.

Underfloor ducts, when laid in concrete floors, are disposed with the upper surfaces of the conduits a substantial distance below the floor level. If provision to the contrary is not made, it is then necessary to break through a substantial thickness of overlying concrete, as well as through the wall of the conduit, in order to obtain access to the interior of the conduit. In order to lessen this difiiculty, access plugs have been mounted in closely spaced positions on the upper wall of a conduit, to extend a substantial distance upwardly toward the floor surface, so that, as the duct isembedded in the concrete floor, no more than a thin skin of concrete overlies theplug,

When it is desired to obtain an outlet at any point where prospective outlet is so provided, the skin or shell of concrete is broken, and the plug is withdrawn, thus leaving an opening extending downwardly from the surface of the floor to the upper surface of the conduit. A bushing or fitting is then inserted in the opening left by removal of the plug, so that the conductors in the conduit may be drawn through the fitting to be led to a desired point of connection, or connected to a receptacle mounted in the bushing. It has been previous practice to taper the plugs, so that they may be readily withdrawn.

An object of my invention is to provide an access element, of simple and inexpensive structure, which, when mounted upon the conduit of an underfloor duct, may remain in position in a floor of concrete or the like, and keyed to the concrete of the floor, when access is had to the interior of the conduit through the element; thus providing a lining wall or shell in the floor opening through which access is had.

Other objects of my invention are to provide an access element for the designated purpose, which may be readily applied in installation of the underfloor duct at Various selected points along a length of conduit in accommodation to the probable necessity for obtaining outlet at various points along the conduit; and which may be readily adjusted in installation to the depth of concrete, or similar floor material, which is to overlie the conduit. 7 r

Still another object of my invention is to provide an access element which is firmly held against movement relatively to the conduit on which it is mounted by resilient engagement with engaging means of simple form carried by theconduit.

In the accompanying drawing Fig. I is a fragmentary plan View of an underfloor duct, showing the access element of my invention on one region of the conduit, and showing the conduit as prepared for the mounting of my access element thereon in other regions of the conduit.

Fig. II is a view, of the underfloor duct, showing the conduit partially in side elevation and partially broken away; and showing the access 7 element mounted thereon in central, vertical section, the relation of the elements shown being identical with the showing of Fig. I.

Fig. III is a vertical section through a floor of concrete, or generally similar material, showing a fragment of an underfloor duct comprising a conduit and my access element thereon in the condition existent pending the use of the access element in obtaining access to the interior of the conduit.

Fig. IV is a view, taken on a plane perpendicular to the plane of Fig. III, showing the floor and conduit in section, and showing the access element keyed in the floor, and serving as a liner for an opening leading to the conduit from the upper wall of which a section has been drilled, or otherwise removed.

In the drawing, reference numeral I designates a conduit which is of substantial wall thickness, and is of the single-piece type. Threaded into the upper wall Id of the conduit are screws 2, spaced at intervals along the conduit, and so set in the upper wall thereof that the head of each screw is spaced a substantial distance from the upwardly presented surface of the upper conduit wall la. Adjacent each of the screws 2, and in longitudinal alignment with it, is a small opening, or indentation, 3, the function of which will be hereinafter described.

The body of the access element comprises a cylindrical shell 4, which is of light-gauge material, and which is bodily threaded to provide threads exteriorly, as well as interiorly, thereof. A second shell element 5, also of light-gauge material, and also threaded bodily, is shown as screwed into the shell 4. The distance to which the upper shell element 5 is caused to extend into the lower shell element determines the combined vertical extent of these elements, and thus provides a substantial adjustability to vary the height of the access element as a whole.

The shell element 4 has a bottom wall 6, which is centrally and circularly indented at I. In this central indented region of the bottom wall or base of shell 4 is a key slot 8, the enlarged region of which is adapted to pass over the heads of the screws 2, and the restricted region of which is adapted to embrace the screw shank. In mounting one of the access elements on the conduit, it is placed thereon with the head of one of the screws 2 projected through the enlarged region of the key slot, and is shifted laterally into a position in which the head of the screw overlies the restricted, shank-embracing region of the slot.

The annular region 9 of the shell floor is downwardly deformed to provide a boss I0, formed to engage in the hole or indentation 3 in the upper wall of the conduit. This boss I0 is so positioned, with respect to the key slot 8, that it engages in the hole or aperture 3 when the shell 4 is in such position that the shank of the screw on which the shell is mounted is embraced by the restricted region of the key slot. This engagement resists turning movement of the shell 4. At the region in which the form of the key slot 8 changes, I deform the metal upwardly at the edges of the key slot to form protuberances 8a over which the head of the screw passes in its travel to engaging position; this arrangement provides a snap engagement which resists lateral displacement of the shell along the key slot 8.

The light-gauge material of which the access element is made possesses resiliency, and is desirably a resilient metal. Since the central region I of the access element is upwardly deflected or indented to bring it into cooperative relation with the head of screw 2, a resilient snap engagement between the cover and screw is made when the access element is brought into engaging position. This effect is intensified if the length of the screw shank, lying between the upper surface of conduit wall Ia and the head of the screw, be made slightly less than the depth of the indented region in the bottom 6 of the access element.

When the access element is being mounted on the conduit, the contact of boss ID with the upper face of the conduit wall increases the resilient deformation of the access element bottom, and

contributes to the effect of a snap engagement between the access element and the conduit when the boss registers with its cooperative hole or indentation 3 in the conduit wall.

Referring to Fig. III of the drawing, the conduit I, and the access element, therein designated as a whole by reference letter A, are shown embedded in a floor B of concrete, or the like, with a relatively thin layer or skin b of the floor material overlying the access element. In this position, the location of the access element in the floor is indicated by a marker carried by the access element and extended to the floor surface, this marker being shown as a screw II.

To prepare the access element for formation of the floor material therearound and thereover, a cover is first positioned in the shell 5. This cover, or diaphragm, is a dish-shaped element, of generally cylindrical contour, having a base I2, a vertical, circular wall I3, and a peripheral flange or lip I4 adapted to engage a bead I5 formed at the upper edge of the shell 5.

The cover, or diaphragm, is also formed of light-gauge material, and possesses resiliency. In order to increase the yielding qualities of the cover, the base I2 of the cover is provided with a plurality of slots I6, extending radially inward from the vertical wall I3, and extending upwardly throughout a portion of the wall height. The marking screw II, to which reference has been above made, is carried by the base I2 of the cover in position to project upwardly beyond the cover and the shell 5.

This cover, or diaphragm, is generally similar to the corresponding element, disclosed in Letters Patent of the United States No. 1,898,087, issued to me February 21, 1933, and presents the advantage that, in yielding to blows upon the overlaying layer of concrete, it facilitates the operation of breaking or chipping this layer in establishing access to the conduit.

Fig. IV of the drawing illustrates a condition in which access has been obtained to the conduit I, through the upper wall Ia of the conduit, and by way of the access element or cup A. In so doing, the thin layer or skin of floor material b, which overlaid the access element, has been chipped or hammered away, and the cover of the access element has been removed. By use of suitable means, such by preference as an annular drill, the base of the lower shell element 4 has been cut out, and an opening I! has been cut through the upper wall Ia of the conduit. In drilling, I prefer to use a composite drill having a central bit and a concentric toothed annulus surrounding the bit. By removing screw 2 from position on the conduit wall, an opening is provided in which the bit of the drill may be inserted to center the drill, with the annular toothed region of the drill lying in the annular trough I8 which surrounds the centrally deflected region I in the bottom wall 6 of the access element.

As shown in Fig. IV, the complete cylindrical shell formed of shell element 5, and the remaining portion of shell element 4, may remain in position in the floor material, being interlocked therein by the corrugated effect provided by the bodily threading of the shell element. It may be broken loose and removed from the opening, but it is desirable to leave the circular shell in position to serve as a sleeve or liner in the opening leading to the interior of the conduit. As shown, in Fig. IV of the drawing, the interior of the conduit is accessible from above the floor level, so that conductors may be drawn therefrom, and any desired fitting may be installed.

As shown and described, screws set in the upper wall of the conduit are used for attachment of the access element thereto. It is to be understood, however, that any suitably headed protuberance, such as a headed rivet or headed pin welded to the conduit wall, may alternatively be employed. In such instances the protuberances may be cut close to the conduit wall to permit centering of a composite drill. Other obvious alterations in the form and arrangement of the parts may be made within the ambit of my invention, as defined in the appended claims. For example, a protuberance corresponding to the boss 9 may, if desired, be provided on the upper wall of the conduit, and a depression corresponding to the indentation 3 in the conduit wall may be formed in the floor of the access element. This reversal similarly provides snap engagement of the access element on the conduit.

I claim as my invention:

1. An access element for attachment to the plane uninterrupted upper wall of a metallic conduit to provide in an underfloor duct for electrical conductors a passage to the conduit through floor material in which the duct is embedded comprising a cylindrical shell of light-gauge resilient metal formed exteriorly to key with the til material of the floor and having an under Wall slotted to receive and resiliently to engage conduit-carried projection in mounting of the access element on a conduit, said under wall of the access element being regionally deformed downwardly to provide a boss adapted to engage a recess in the wall of the conduit.

2. In an underfloor duct the combination of a metallic conduit having on the upper wall thereof which is uninterrupted and is formed to lie in a single plane a headed engaging member with the head thereof spaced from the Wall of the conduit with an access element formed as a resilient shell having a resilient bottom wall presented to the conduit and regionally deflected upwardly away from the adjacent wall of the conduit, and a slot in the upwardly deflected region of the said bottom wall formed to receive and engage the head of the said conduit-carried engaging member.

3. In an underfloor duct the combination of a metallic conduit having on the upper wall thereof which is uninterrupted and is formed to lie in a single plane a headed engaging member with the head thereof spaced from the wall of the conduit with an access element formed as a resilient shell having a resilient bottom wall presented to the conduit and regionally deflected upwardly away from the adjacent wall of the conduit, a slot in the upwardly deflected region of the said bottom wall formed to receive and engage the head of the said conduit-carried engaging member, a downwardly projected boss carried on the undeflected region of the said bottom wall, and a depression in the adjacent Wall of the conduit positioned cooperatively with respect to said boss, said boss and depression cooperatively providing additional resilient engagement between the access element and the conduit in cooperative engagement between the headed engaging member on the conduit and the slot in the resilient bottom wall of the access element.

4. An access element for attachment to the plane uninterrupted upper wall of a metallic conduit to provide in an underfloor duct for electrical conductors a passage to the conduit through floor material in which the duct is embedded comprising a cylindrical shell of light-gauge resilient metal having an under wall slotted to receive and resiliently to engage conduit carried projection on a conduit, in combination with a one-piece metallic conduit as above defined and equipped with an access element engaging projection, said conduit and said access element having additionally a boss on one of said elements and a depression in the other arranged in conduit-mounted position of the access element cooperatively to engage and firmly to position the access element on the conduit.

5. In an underfloor duct the combination of a rigid metallic one-piece conduit having a plane uninterrupted upper wall and a headed engaging member secured to said plane upper wall with the head thereof spaced from the outer wall surface with an access element formed as a resilient shell having presented to the conduit a resilient bottom comprising within the ambit of the shell means adapted resiliently to engage the access element with said headed member and to the upper conduit wall to which said headed element is secured.

6. In an underfloor duct the combination of a rigid metallic one-piece conduit having a plane uninterrupted upper wall and an engaging member projected upwardly therefrom with an ac cess element formed as a resilient circular shell having at the base thereof a resilient structure disposed in a general plane parallel to the plane upper wall of said rigid metallic conduit and adapted resiliently to engage with the projection from said conduit wall thereby to engage the access element thereto.

JAMES M. G. FULLMAN. 

